metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 on the Mohs scale. Color: White, grey, brownish, light yellow. Luster: Vitreous to greasy. Fracture: Conchoidal to uneven. Cleavage: None. Specific gravity: ~2.65.
- Hardness
- 7 on the Mohs scale
- Color
- White, grey, brownish, light yellow
- Luster
- Vitreous to greasy
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Physical properties
Hardness: 7 on the Mohs scale. Color: White, grey, brownish, light yellow. Luster: Vitreous to greasy. Fracture: Conchoidal to uneven. Cleavage: None. Specific gravity: ~2.65.
Formation & geological history
Formed through the regional or contact metamorphism of quartz-rich sandstone under extreme heat and pressure, causing the original quartz grains to recrystallize into a interlocking mosaic.
Uses & applications
Used as a decorative stone in landscaping, dimension stone in building construction, crushed stone for railway ballast, and as a source of silica for glassmaking and metallurgy.
Geological facts
Quartzite is so tough that when it breaks, it fractures through the individual quartz grains rather than along the boundaries between them, unlike its precursor sandstone.
Field identification & locations
Can be identified in the field by its extreme hardness (scratches glass easily) and sugary to glassy fused appearance. Very common in mountainous metamorphic terrains worldwide.
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